Corrosion inhibition compositions containing substituted diamine phosphonates and processes for using the same

ABSTRACT

WHEREIN R1, R2, R3, R4, X, Y and Z are hereinafter defined and n is 0 - 10, alone or in combination with zinc, dichromates, certain thiols, 1,2,3-triazoles, silicates, inorganic phosphates, molybdates, tannins, lignins, lignin sulfonates, certain calcium and magnesium salts and mixtures thereof, are disclosed as inhibiting the corrosion of metals by oxygen-bearing waters.   Substituted diamine phosphonates of the general formula

United States Patent 1 1 Mitchell 1 Mar. 27, 1973 CORROSION INHIBITIONCOMPOSITIONS CONTAINING SUBSTITUTED DIAMINE PHOSPHONATES AND PROCESSESFOR USING THE SAME [75] Inventor: Robert S. Mitchell, Webster Groves,

[73] Assignee: Monsanto Company, St. Louis, M0.

[2 2 Filed: May 17, 1972 [21] Appl. No.: 254,008

[52] U.S. Cl. ..252/389 A, 21/27 A, 106/14, 210/58, 252/181, 252/387,252/389 R,

[51] Int. Cl. ..C23f 11/16 [58] Field of Search ..252/389 A, 389 R, 387,181, 252/390; 21/27, 2.5; 260/5025; 106/14;

[56] References Cited UNITED STATES PATENTS 2,961,311 11/1960 Bersworthet al. ..260/502.5

3,160,632 12/1964 Toy et al. ..260/502.5 3,298,956 1/1967 Irani et al...260/502.5

3,336,221 8/1967 Ralston ..260/502.5 3,395,113 7/1968 Irani et a1...260/502.5

Hwa ..252/387 Hatch ..252/389 A Primary Examiner-Leon D. RosdolAssistant Examiner-Irwin Gluck Att0rney-James J. Mullen et a1.

[57] ABSTRACT Substituted diamine phosphonates of the general formula Hl/ R10P? R: Y

34 Claims, No Drawings CORROSION INHIBITION COMPOSITIONS CONTAININGSUBSTITUTED DIAMINE PHOSPHONATES AND PROCESSES FOR USING THE SAME Thepresent invention relates to corrosion inhibiting compositions and tomethods of inhibiting the corrosion of metal surfaces in contact with anaqueous medium of a corrosive nature. More particularly, this inventionrelates to methods of inhibiting the corrosion of metal surfaces byutilizing in the corrosive aqueous medium certain substituted diamineseither alone or in combination with a water-soluble zinc salt, adichromate, certain thiols, 1,2,3-triazoles, silicates, inorganicphosphates, molybdates, tannins, lignins,, lignin sulfonates, certaincalcium and magnesium salts and mixtures thereof.

The present invention has special utility in the prevention of thecorrosion of metals which are in contact with circulating water, thatis, water which is moving through condensers, engine jackets, coolingtowers, evaporators or distribution systems, however, it can be used toprevent the corrosion of metal surfaces in other aqueous corrosivemedia. This invention is especially valuable in inhibiting the corrosionof ferrous metals including iron and steel (also galvanized steel) andnonferrous metals including copper and its alloys, aluminum and itsalloys and brass. These metals are generally used in circulating watersystems.

The major corrosive ingredients of aqueous cooling systems are primarilydissolved oxygen and inorganic salts, such as the carbonate,bicarbonate, chloride and/or sulfate salts of calcium, magnesium and/orsodi- It is, therefore, a primary object of this invention to providenew corrosion inhibiting methods.

It is another object of this invention to provide new corrosioninhibiting methods for ferrous metals including iron and steel andnon-ferrous metals including copper and brass.

It is another object of this invention to provide new and corrosioninhibiting methods for ferrous metals including iron and steel andnon-ferrous metals including copper and brass in contact with an aqueouscorrosive medium It is another object of this invention to provide newcorrosion inhibiting methods for ferrous metals including iron and steeland non-ferrous metals including copper and brass in contact withcooling waters.

Other advantages and objects of the present invention will be apparentfrom the following discussion and appended claims.

It has been found that certain substituted diamines corresponding to thefollowing formula unexpectedly function as corrosion inhibitors whenused alone or in combination with zinc, dichromate, certain thiols and1,2,3-triazoles, silicates, inorganic phosphates, molybdates, tannins,lignins, lignin sulfonates, certain calcium and magnesium salts andmixtures thereof in aqueous or water systems containing metals or incontact with metals.

ln Formula I above, R, and R can be alike or unlike and are from thegroup metal ion or hydrogen or any cation which will yield sufficientsolubility for the desired enduse. The aforementioned cations are fromthe group of metals alkali metals such as sodium, lithium, potassium,alkaline earth metals such as calcium and magnesium, aluminum, zinc,cadmium, manganese, nickel, cobalt, cerium, lead, tin, iron, chromium,and mercury. Also included are amines such as ammonium ions and alkylammonium ions. In particular, those alkyl ammonium ions de'rived'fromamines having a low molecular weight, such as below about 300, and moreparticularly the alkyl amines, alkylene amines, and alkanol aminescontaining not more than two amine groups, such as ethyl amine, diethylamine, propyl amine, propylene diamine, hexyl amine, 2-ethylhexylamine,N-butylethanol amine, triethanol amine, and the like, are the preferredamines. It is within the scope of the present invention to includeamines, such as those described in U.S. Pat. Nos. 3,613,788 and3,619,427 (which are incorporated herein by reference), in order toprovide the amine saltsof the aforesaid substituted diamines (FormulaI). It is to be understood that the preferred metal ions are those whichrender the compound a water-soluble salt, e.g., sodium, inconcentrations sufficient for the desired applications.

In Formula I, it is to be understood that this includes salts, partialsalts, acid and partial acids.

In Formula I above, R and R are alike or unlike and are eachindependently an alkylene group containing from two to five, preferablytwo to three carbon atoms. Examples of such alkylene groups include,without limitation, ethylene, propylene, butylene and the like.

In Formula I, and partial Formula II above, X and Y are each alike orunlike and are from the group hydrogen and organic radicals such asalkyl containing less than 40, preferably one to four, carbon atoms. Itis to be understood that organic radicals such as other aliphatic groupsand also aromatic groups are included herein. X and Y are preferablyhydrogen.

In Formula I, Z is a hydrocarbon group containing from two to l5 carbonatoms and includes (a) normal or straight chain carbon groups, e.g., (CHto (CI-I (b) branched chain carbon groups, e.g., CH,CH,CH and (c) cycliccarbon groups, e.g.,

In Formula I, n has a value of from 0 through 10 (preferably 0 3). It isto be understood that all of the compounds falling within the aboveFormula I and as heretofore defined are generically described herein assubstituted diamines or SDA. In other words, then, the acids, salts andphysical and chemical mixtures thereof are all generically describedherein as substituted diamines or so/a."

Illustrative (but without limitation) of some of the R. .L O XN-Z-NKRgOMtRrOHHz II I/ R10PCl3 R2 Y Compound No. R R, R R, X Y n Z l HH C H, H H 0 (CH 2 K n u u 0 u 3 N Na u n u 0 u 4 u ZN u 0 u 5 NH4 u .i0 t. 6 H C H, l 7 u u i u i. 5 u 8 i. u u .l u u 9 u u CaHs 03Ha it u lu 10 u Na .i u u l i. ll H 5 12 i. u (32H4 I 3 u u u u 5 14 Na C,H l 15H K 3 l6 H CH 0 17 u t. CHI 0 u l8 C H H H 0 l9 u CZH u 0 (CH2)z 20 i. ui. u i. 0 (CHU 21 i. u u n u 0 (cnos 22 0 (CH,), 23 t. n u 0 can" 24 u uu .t 0 CHH The SDA falling within the aforegoing Formula I are preparedaccording to the disclosure set forth in my copending patent applicationSer. No. 254,247 filed May 17, 1972 and filed concurrently herewith andwhich is incorporated herein by reference.

It has been found that to effectively inhibit corrosion, at least 3parts per million, preferably from about 10 parts per million (ppm) toabout 500 parts per million, more preferably from about 10 parts permillion to about 150 parts per million, of the SDA should be utilized inthe corrosive medium. It is to be understood that greater than 500 ppmof SDA can be utilized where one so desires as long as the desired endresult is substantially achieved or these higher amounts are notdetrimental to the water system. Amounts as low as 1 ppm are found to beeffective.

The SDA corrosion inhibitors of the present invention are effective inboth an acidic or basic corrosive media. The pH can range from about 4to about 12. For example, compound No. l, heretofore set forth, whenused in amounts from about 3 parts per million to about 100 parts permillion is an effective corrosion inhibitor in a corrosive medium wherethe pH is from about 4 to about l2.

In conjunction with the utilization of the SDA per se as corrosioninhibitors, it has also been found that there exists a cooperativeeffect on corrosion inhibition between the SDA and the zinc ion; thatis, the use of the SDA with the zinc ion more effectively inhibitscorrosion than does an equal concentration of the SDA or the zinc ionalone. (The zinc ion is used in the same concentration as the SDA, e.g.,a suitable corrosion inhibitor may consist of 50 ppm of zinc ion plus 50ppm of said SDA.) It is to be understood, then, that the presentinvention also encompasses a corrosion inhibition compositionscontaining a mixture of the SDA and a zinc-containing material (i.e., awater-soluble zinc salt) which is capable of forming the zinc ion in anaqueous solution.

Illustrative examples of the zinc-containing material (water-solublezinc salt) which are set forth for exemplary purposes only and hencenon-restrictive, include zinc acetate, zinc bromate, zinc benzoate, zincborate, zinc bromide, zinc butyrate, zinc caproate, zinc carbonate, zincchlorate, zinc chloride, zinc citrate, zinc fluoride, zinc fluosilicate,zinc formate, zinc hydroxide, zinc d-lactate, zinc laurate, zincpermanganage, zinc nitrate, zinc hypophosphite, zinc salicylate, zincsulfate and zinc sulfite. The preferred water-soluble zinc salt is zincsulfate. It is to be understood that it is within the scope of thepresent invention that the zinc ion can be supplied in part or wholly byusing the zinc salt of the acid form of the SDA.

The SDA and the zinc containing material, which is, in essence, awater-soluble zinc salt, may be mixed as a dry composition and can befed into a water system containing the metals heretofore described to beprotected. Such a composition having a maximum cooperative effectbetween the SDA and the zinc ion containing material comprises fromabout l0 percent to about percent by weight of the water-soluble zincsalt and from about 20 percent to about percent by weight of the SDA,all weights being predicated upon the total weight of the mixture.Preferably the weight of the composition comprises from about 20 percentto about 60 percent by weight of the water-soluble zinc salt and fromabout 40 percent to about 80 percent by weight of the SDA.

a combination of about 3 to ppm A combination the SDA and about 2 toabout 100 ppm zinc ion will inhibit corrosion in most water systems; themost preferred concentration range is about 5 to 25 ppm SDA and about 5to 25 ppm zinc ion. It is to be understood, however, that thoseconcentrations are not in any manner meant to limit the scope of thepresent invention.

It has also been found that a cooperative effect exists between the SDAand chromate or dichromate. Because chromate and dichromate are eachreadily converted into the other by a change in pH, it is understoodthat both will be simultaneously present at most pHs, even though onlyone is mentioned.

Corrosion in most water systems may be inhibited by adding from about 1to about 100 ppm of SDA and from about 1 to about 100 ppm of thechromate or dichromate; preferably from about 5 to 25 ppm SDA and fromabout 5 to 25 ppm chromate or dichromate is added. It is to beunderstood that larger amounts or smaller amounts of each material canbe utilized if one so desires.

Suitable chromates for use in the composition and process of thisinvention include, for exemplary purposes only, sodium dichromatedihydrate, anhydrous sodium chromate, sodium chromate tetrahydrate,sodium chromate hexahydrate, sodium chromate decahydrate, potassiumdichromate, potassium chromate, ammonium dichromate, and chromic acid.In other words, the chromium compound used is any water-solublehexavalent compound of chromium and is preferably an alkali metalchromate or dichromate heretofore described.

In most cases, an effective corrosion inhibition composition contains amixture of from about 1 percent to about 60 percent and preferably fromabout percent to about 40 percent, of the water-soluble inorganicchromate, based on the combined weight of the chromate and SDA. The useof chromates per se is further described in U.S. Pat. No. 3,431,217 andthe publications cited in this patent, all of which are incorporatedherein by reference.

It has also been found that compositions of the SDA, zinc ion, andchromate or dichromate are useful in inhibiting the corrosion of metals.The inhibiting action of zinc (supplied in the form of a water-solublezinc salt heretofore mentioned) and dichromate compositions has beenshown in U.S. Pat. No. 3,022,133, which is incorporated herein byreference. Thus, all three components of this composition arecooperatively effective. The coaction of zinc and dichromate illustratedin U.S. Pat. No. 3,022,133 remains unaffected in the presence of the SDAand the other ingredients of the inhibitor compositions mentionedherein. In other words, then, it is within the scope of the presentinvention to provide a corrosion inhibiting composition containing theSDA, a water-soluble zinc salt and a chromate and/or dichromate.

Especially useful combinations of SDA, chromate and zinc exist in therange of from about 1 to about 100 ppm of SDA, from about as to about 50ppm of the chromate or dichromate, and from about '75 to 50 ppm of thezinc ion. The preferred range is from about 2 to 30 ppm SDA, and fromabout 1 to ppm chromate or dichromate, and from about l to about 15 ppmzinc Where the water systems are in contact with various metals such assteel, copper per se or copper-containing metals, it is desirable touse, along with the SDA (either alone or in combination with the zincion and/or dichromate or chromate), a 1,2,3-thiozole or a thiol of athiazole, an oxazole, or an imidazole as described respectively in U.S.Pat. Nos. 2,941,953; 2,742,369; and 3,483,133; all of which patents areincorporated herein by reference. These azoles are referred to herein asthiols and 1,2,3-thiazoles. These thiols and 1,2,3- thiazoles are foundeffective in inhibiting the attack of the SDA on copper.

The preferred 1,2,3-triazole is 1,2,3-benzotriazole of the formula Thepreferred thiols of a thiazole, an oxazole, or an imidazole areZ-mercaptothioazole Z-mercaptobenzothiazole and Z-mercaptobenzimidazoleTheamounts of thiol or 1,2,3-thiazole used will depend upon theparticular water system. Where the water system containing copper is anopen or once through system from about 3 to about 100 ppm SDA, about0.05 to 5 ppm thiol or 1,2,3-triazole, and up to about 100 ppm zinc ionare generally satisfactory concentrations; preferably the concentrationsare about 5 to 25 ppm SDA, about 0.5 to 2 ppm triazole or thiol, andabout 5 to 25 ppm zinc ion.

A dry composition may be made which may be fed into the water systemcontaining copper. Such a composition would consist of about 20% to byweight, based on the total weight of said composition, SDA; about 1% to10% by weight thiol or 1,2,3-triazole, and up to about 79% by weightsoluble zinc salt; preferably, it would consist of about 38% to 90% byweight SDA, about 2% to 10% by weight thiol or 1,2,3-triazole, and up toabout 60% by weight soluble zinc salt.

It is within the scope of the present invention that the corrosioninhibitors (SDA) of this invention may be used in conjunction with othermaterials (water treating chemicals); in some instances, there can be acooperative effect therebetween. The following is a list of thesematerials and publications wherein such materials are utilized in asimilar fashion in conjunction with corrosion inhibition.

1. Water-soluble polycarboxylic acids from the group adipic, succinic,azelaic, suberic, sebacic, pimelic, and glutoric acids andhydroxypolycarboxylic acids having from four to 10 carbon atoms and atleast 2 carboxylic acids or an alkali metal or ammonium saltthereof-note British Pat. No. 1,230,172;

. Acetodiphosphonic acids and salts thereof-note German Pat. No.2,115,427;

3. Lignins, lignosulphonate, starch, sodium mannuronate, agar-agar,polyelectrolytes which contain the group in which R is nitrile, amide,carboxyl or carboxyalkyl and which have a molecular weight of 5,000 to15,000,000 and water-soluble salts thereof-note U.S. Pat. No. 3,547,817;

4. Amino tri(methyl phosphonic acid) and monoand poly-phosphonicacids-note U.S. Pat. No. 3,510,436;

5. Polyacrylic acid, polyacrylamide or partially hydrolyzedacrylamidenote U.S. Pat. No.

. Aminomethyl phosphonic acid compounds such as those described in U.S.Pat. No. 3,483,133;

7. Derivatives of methanol phosphonic acid or methanol diphosphonicacids such as those described in U.S. Pat. No. 3,532,639;

8. The phosphorus-containing polar organic liquids described in U.S.Pat. No. 3,637,790;

9. Leucocyanidin-catechin polymers, carbamates and sodium bisulfatewhich are described in U.S. Pat. No. 3,518,203;

10. Lignosulfonate mixed sugar aldonate polymeric materials such asthose described in German Pat. publication No. 2,123,808;

11. Ethylene oxide-propylene oxide polymeric corrosion inhibitioncompositions containing phosphates, borates, nitrites, silicates andbenzoates such as described in German Pat. publication No. 2,054,506;

12. l-hydroxy ethylidene-l,l-diphosphonic acid and water-solubleorthophosphates such as those described in British Pat. No. 1,243,347;

13. A water-dispersible tannin compound and a HCN modified lignosulphateand/or an HCN modified naphthalene sulphonate such as those described inBritish Pat. No. 1,244,123;

14. Silicate materials such as those described in U.S.

Pat. No. 3,630,930;

15. Polyfunctional phosphated polyol esters such as those described inU.S. Pat. No. 3,580,855;

16. Sulfonated [ignites such as those described in U.S. Pat. No.3,629,105;

17. The polyphosphonic acids such as those described in U.S. Pat. No.3,619,427; 18. Molecularly dehydrated phosphates and phosphonates suchas those described in U.S. Pat. No. 3,483,133;

19. Molybdates such as those described in An Electrochemical Study ofI-leteropoly Molybdates as Cooling Water Corrosion Inhibitors, A.Weisstuch and CE. Schell, Paper No. 104 presented at the March, 1972annual meeting in St. Louis, Mo. of the National Association ofCorrosion Engineers (NACE).

20. Inorganic Phosphates including orthophosphates.

21. Calcium and magnesium salts such as calcium or magnesium chlorides,sulfates, nitrates and bicarbonates.

22. Cationic organic compounds such as those described in German Pat.publication No. 2,063,208 and German Pat. publication No. 2,063,209.

23. Fluidizing polymers such as those described in The Oil And GasJournal, July 5, 1971, pages 104-5; Plant Engineering, Dec. 1965, pages133-5; and Chemical Engineering, Dec. 6, 1965, pages 164-8.

24. The scale and corrosion inhibitors such as those described in U.S.Pat. Nos. 3,123,640; 3,123,641; 3,141,905; 3,462,365; 3,477,956;3,480,083; 3,487,018; 3,518,204; 3,580,855; 3,591,513;

3,592,764; 3,592,834; 3,596,766; 3,617,578; 3,620,974; and 3,644,205.25. And mixtures of the above materials listed in items 1 through 24.All of the above publications are to be considered as incorporatedherein by reference.

In conjunction with the Examples hereinafter set forth, two tests areconducted to determine the effectiveness of the corrosion inhibitors ofthe present invention in different corrosive media, i.e., ordinary tapwater and synthetic cooling tower water.

Test 1 is conducted at room temperatures, about F., wherein severalcoupons of mild steel (S.A.E. 1018) having dimensions of 5 cm X 3.5 cm X0.32 cm are thoroughly cleaned using a commercially available cleansingpowder and rinsed with distilled water and acetone. After the couponsare weighed, they are mounted on brackets and continuously immersed andremoved from the corrosion composition, i.e., ordinary tap water, sothat the coupons remain immersed in the composition for 60 seconds andthen remained out of solution, exposed to air for 60 seconds. Thisprocedure is continued for a definite length of time (in hours) afterwhich the coupons are withdrawn and the corrosion products on thecoupons are removed by using a soft brush.

The coupons are rinsed with distilled water and acetone and thenreweighed. The loss in weight (in milligrams) is then appropriatelyinserted into the equation:

KW/DAT Corrosion in mills per year wherein W weight loss during tests inmilligrams;

D specific gravity of the metal;

A exposed surface area in square cm; and

T time of exposure to solution in hours K 3 ,402 in order to determinethe corrosion that has taken place expressed in terms of mills ofpenetration per year (m.p.y.). The corrosion rate of the couponsprotected by a corrosion inhibitor can then be compared to the corrosionrate of the unprotected coupons. A decrease in the corrosion rateindicates the effectiveness of the corrosion inhibitor.

In tests of this nature where the aqueous corrosive medium is ordinarytap water at room temperature, any corrosion rate less than thatcorrosion rate of the said medium is desired and rates of less thanabout 2 to 10 m.p.y. are highly desired and substances that give thisrange or lower are considered excellent. This does not mean, however,that substances having a corrosion rate of more than about 2 to 10m.p.y. are not valuable; depending upon the particular conditions acompound or composition having a higher corrosion rate may be used, asin an instance where the equipment will be used, only for a short periodof time.

A cooling water system is constructed on a small scale to approximateconditions for Test 2. From a 5- gallon glass tank containing syntheticcooling water, a hose leads into a 6 in. glass jacket which surrounds amild steel pipe. A hose leads from the jacket into a glass condenser andthen back to the tank. Air is added to the system at the condenser inorder to match an actual operation in which air is absorbed by thecooling water.

Steam is passed through the steel pipe which is enclosed by theglassjacket.

Four mild steel coupons are weighed and then mounted in the tank. Afterexposure the steel pipe is checked visibly for signs of corrosion andthe corrosion rate of the coupons is calculated. Synthetic cooling wateris prepared to approximate actual cooling water as follows:

Ca 200 ppm y+ 55 ppm Na 320 ppm 1- 600 ppm S 500 ppm Hco; 58 p TotalDissolved Solids of Distilled Water 1,733 ppm A circulating coolingwater system contains a high concentration of inorganic salt or ionsmuch higher than ordinary tap water as can be seen from the formulationfor synthetic cooling tower water. Likewise a cooling water system isoperated at high temperatures usually 50 C. or higher. Primarily becauseof these two factors the acceptable corrosion rates in cooling waters isless than about 10 m.p.y. Therefore, corrosion inhibitors havingcorrosion rates less than about 10 m.p.y. are considered good andcommercially acceptable.

The corrosion inhibiting compositions of this invention can bemanufactured via a number of methods which will give good protectionagainst corrosion. For

example, the SDA either in the form of its acid or salt per se or incombination with the water soluble zinc salt, chromate, dichromate,thiols, 1,2,3-thiazole, silicates, inorganic phosphate, molybdate,tannin, lignin, lignin sulfonate, and calcium and/or magnesium salts,can simply be dissolved by intermixing them into the aqueous corrosivemedium. Via another method, they can be dissolved separately in water oranother suitable solvent and then intermixed into the aqueous corrosivemedium.

Various means are available to insure that the correct proportion ofcorrosion inhibitor is present in the corrosive medium. For example, asolution containing the said corrosion inhibitor can be metered into thecorrosive medium by a drop feeder. Another method is to formulatetablets or briquettes of a solid SDA (and other ingredients) and thesecan then be added to the corrosive medium. The said solid, afterbriquetting, can be used in a standard ball feeder so that the solid isreleased slowly into the corrosive medium.

The invention will be further illustrated but is not limited by thefollowing examples:

EXAMPLE 1 Three separate portions consisting each of 600 ml of aqueouscorrosive medium are individually treated with the indicated SDA so thatit contains separately 5, 50 and 100 parts per million of SDA. (Wherethe acid form is used, it is converted to the sodium salt by theaddition of sufficient NaOH to maintain the medium at pH 9.0 to 9.5.)Test 1, as described hereinbefore, is conducted using 1018 S.A.E. mildsteel coupons measuring cm X 3.5 cm X 0.32 cm. The corrosive medium is asample of water obtained from the St. Louis County Water Company havinga pH from about 9.0 to about 9.5 and a hardness of about 100 to about110 parts per million as calcium carbonate. Test 1 is conductedaccording to the procedure hereinbefore outlined for hours. Six hundredml. of the untreated aqueous corrosive medium is tested as a control.The data are illustrated in Table 1.

Test 1 is also conducted on a commercially available corrosioninhibitor, containing somezinc (about 1 to about 4% by weight) butmostly tetra sodium pyrophosphate (about 50 to about 60% by weight);these data are shown in Table 1.

TABLE 1 Corrosion Rates on Mild Steel (S.A.E. 1018) Coupons 5 cm X 3.5cm X 0.32 cm pH 9.0 to 9.5 of the Corrosive Media Concentration TimeCorrosion Corrosion inhibitor ppm (hrs.) Rate (m.p.y.)

Corrosion Medium 96 25.2 SDA Compound No.

l 5 96 8.9 l 50 96 5.3 1 96 3.7 6 5 96 10.2 6 50 96 8.1 6 100 96 4.9 9 596 6.7 9 50 96 4.1 9 100 96 3.8 12 5 96 9.8 12 50 96 6.2 12 100 96 5.116 5 96 10.9 16 50 96 5.9 16 100 96 3.8 18 5 96 9.9 18 5O 96 5.2 18 10096 3.6 20 5 96 10.4 20 50 96 5.0 20 100 96 3.1 23 5 96 8.7 23 50 96 5.323 100 96 3.6 Corrosion Medium 96 29.6 Zinc Tetra Sodium Pyrophosphate(Zinc 1% to 5 96 15 4%, tetra sodium pyro- 50 96 6.8 phosphate 40% to60%) 100 96 4.1

The data in Table 1 show that the SDA are an effective corrosioninhibitor. Table 1 shows that these SDA are at least as .good as and insome cases superior to the commercially available zinc tetra sodiumpyrophosphate inhibitor. As pointed out before, substances that reducethe corrosion rates of mild steel to less than about 10 m.p.y. inordinary tap water are considered excellent. Therefore, it can readilybe appreciated that the SDA of the present invention are effectivecorrosion inhibitors.

EXAMPLE 11 Test 2, as described hereinbefore, is conducted to determinethe effectiveness of the indicated SDA (Example l) as a corrosioninhibitor in cooling water. Example I solutions are individually addedto the five gallon tank containing about 16,000 ml. of synthetic coolingtower water (having a flow rate of 2,750 ml./min.), as set forth above,so that said water contains 5, 50 and 100 parts per million of the SDA.The temperature of the synthetic cooling water is 50 C. Mild steelcoupons (ASTM A-285) measuring 2.5 cm X cm X .6 cm are cleaned with acommercially available cleansing powder and weighed. They are thenmounted on brackets in the five gallon tank. After exposure, they arereweighed and their corrosion rates are calculated.

A blank solution containing no SDA is used as a control to determine thecorrosion rates of mild steel coupons in untreated synthetic coolingtower water. i

The data show that the SDA corrosion inhibitors at greater than 50 ppmreduce the corrosion rate to less than m.p.y. (the control corrosionmedium is about 24.6 m.p.y.), which is the generally acceptable rate fora corrosion inhibitor.

A visual inspection of the mild steel pipe through which the steampasses and which is cooled by the synthetic cooling water treated withSDA shows a very minute amount of corrosion, another indication of theeffectiveness of the novel compound of the present invention.

A commercial corrosion inhibitor containing 2 to 4 percent by weight ofzinc and 40 to 60 percent by weight of tetra sodium pyrophosphate, isused to treat the synthetic cooling water and is tested in the samemanner as Example II. The corrosion rates of the coupons are more than10 m.p.y. and a significant amount of corrosion forms on the mild steelpipe through which the steam passes.

It can readily be appreciated that these SDA are good corrosioninhibitors when used in cooling waters and especially when used inheat-exchanging systems.

EXAMPLE III Example I (above) is repeated with the exception that inaddition to the SDA (5, 500 and 100 ppm) corrosion inhibitor, there isadded sufficient amounts of zinc sulfate in order to providerespectively 5, 50 and 100 ppm of zinc ion in the corrosion medium. Thiscorrosion inhibition composition, i.e., the indicated SDA plus the zincsulfate, shows that at all three concentrations (i.e., 5, 50 and 100 ppmof each) the corrosion rates are substantially less than the ratesusing' the corrosion medium without this mixture and is on the average25 percent less than those rates obtained using only the SDA per se.

EXAMPLE IV Example I (above) is repeated with the exception that inaddition to the SDA (5, 50 and 100 ppm) corrosion inhibitor, there isadded respectively 5, 50 and 100 ppm sodium dichromate to thecorrosionmedium.'This corrosion inhibition composition, i.e., the indicated SDAplus the sodium dichromate, shows that at all three concentrations(i.e., 5, 50 and 100 ppm of each), the corrosion rate is less than therate using the corrosion medium without this mixture and is on theaverage about 11 to percent less than those rates obtained using onlythe SDA per se.

EXAMPLEV A series of separate and individual corrosion inhibitorsconsisting of a mixture of the indicated SDA (60% by weight), zincsulfate (20 percent by weight) and sodium dichromate (20% by weight) areprepared. Example I (above) is then repeated utilizing the abovemixture. The resultant data shows that the corrosion rates using thismixture are substantially less than the rates using the corrosion mediumwithout this mixture and is on the average about 30 to 40 percent lessthan those rates obtained using only the SDA per se.

EXAMPLE VI The corrosion inhibitors are described in the above Examples1, III, IV and V are separately and individually tested in boiler waterfor their separate corrosive inhibiting effect on red brass and mildsteel. The boiler water contains approximately 30-60 parts per millionphosphate and approximately 30-60 parts per million sulfate having a pHof about 14. The corrosive tests are carried out at a temperature of 314C. at 1,500 psig and with a 50 parts per million of the respectivecorrosion inhibitor. In each test, approximately 1 liter of boilerblow-down water is charged into a 2 liter bomb and 1 ml. of a stocksolution is added to give approximately 50 parts per million of thecorrosion inhibitor. Duplicate coupons of mild steel and red brassmeasuring 5 cm X 3.5 cm X 0.32 cm are scrubbed with a commerciallyavailable cleansing powder and weighed. The coupons are then mounted 'oninsulated brackets so that two coupons are in the liquid phase and twocoupons are in the vapor, phase. After sealing the bomb, the cycle ofpumping down with a vacuum pump and filling with nitrogen is repeatedfour times. The time of the tests are taken to be roughly from the timethe temperature reached C. after starting to heat till it again reachedthis temperature after turning off the heat.

The results of these tests show that at temperatures above 300 C. therespective corrosion inhibitors significantly reduces the corrosionrates of both .red brass and mild steel either completely immersed inthe cooling waters or in contact with the vapors of acooling watersystem containing the complex. Italso demonstrates the stability of thecorrosion inhibitors of the present invention at elevated temperatures,over 300 C., for extended periods of time.

In each of the following examples, the indicated SDA and zinc compoundare added to the aqueous corrosive medium so that 50 partsper million ofeach is present.

EXAMPLE VIII Ingredients Parts Aqueous corrosive medium 80,000 SDACompound No. 6 2.6 Zinc sulfate 2.6

EXAMPLE IX 10 Ingredients Parts Aqueous corrosive medium 90,000 SDACompound No. 9 2.3 Zinc sulfate 2.3

EXAM PLE X Ingredients Parts Aqueous corrosive medium 90,000 SDACompound No. l2 2.3 Zinc sulfate 2.3

EXAM PLE XI Ingredients Parts Aqueous corrosive medium 90,000 SDACompound No. 16 2.3 Zinc sulfate 2.3

EXAMPLE XII Ingredients Parts Aqueous corrosive medium 65,000 SDACompound No. 18 L6 Zinc sulfate 1.6

EXAMPLE XIII Ingredients Parts Aqueous corrosive medium 11,000 SDACompound No. 20 2.7 Zinc sulfate 2.7

EX A M PL E X IV Ingredients Parts Aqueous corrosive medium 100,000 SDACompound No. 23 2.5 Zinc sulfate 2.5

EXAMPLE XV A compressed ball of a standard weight and dimension isprepared containing the following ingredients in the quantities noted.

SDA Compound No. l 34 Lignosulfite binder (bindarene) 8 Zinc sulfate 16Inert Ingredients 42 The above composition after briquetting is foundsuitable for mechanically measured addition in water treatment wherein aball feeder is employed.

EXAMPLE XVI Example I (above) is repeated with the exception that coppercoupons are used instead of mild steel coupons and sufficient amounts of1,2,3-benzotriazole to provide 1, 5 and 10 ppm thereof in the corrosivemedia is used in addition to the SDA. Example XVI is repeated again butwithout the benzotriazole material. The data shows that when coppercoupons are used and the corrosive media contains the indicated SDA, thecorrosion rates are less than when the corrosion media does not containsaid SDA. The data further show that use of the benzotriazole with theSDA further reduces the corrosion rate.

It is also within the scope of the present invention to utilizesilicates, particularly inorganic silicates, in combination with theSDA. It is known that silicates are effective corrosion inhibitors asexemplified by Encyclopedia of Chemical Technology," Kirk-Othmer, 1961by The Interscience Encyclopedia, Inc. New York Volume 4, pages 487-529,and Volume 12, pages 268-360; this subject matter is to be considered asincorporated herein by reference. (These silicates can be used in thesame concentration as the watersoluble zinc salts heretofore mentioned.)

It is found in the repeat of the above Example I that the use of acombination of the indicated SDA and a liquid (sodium) silicate (havinga 3.22:l ratio of SiO, to soda) effected a lower corrosion rate thaneither the SDA per se or the silicate per se when used separately.

Thus, it may be seen that this invention relates to the indicated SDAfalling within Formula I above as corrosion inhibitors. We do not intendto be limited to any compounds, composition, or methods disclosed hereinfor illustrative purposes. Our invention may be otherwise practiced andembodied within the scope of the following claims.

What is claimed is:

l. A composition useful for inhibiting the corrosion of metals in awater system consisting essentially of from about 10 percent to about 80percent by weight of a water-soluble zinc salt and from about 20 to 90percent by weight of a substituted diamine having the general formula lRzY wherein (a) R and R are alike or unlike and are selected from thegroup consisting of hydrogen, metal ions, amine ions or any cation whichwill provide sufficient solubility in said aqueous system, mixturesthereof; (b) R and R are alike or unlike and are each independently analkylene group containing from about two to about five carbon atoms; (c)n is an integer having a value of from about to about (d) X and Y areeach alike or unlike and are selected from the group consisting ofhydrogen, aromatic and alkyl; and (e) Z is a hydrocarbon groupcontaining from two to carbon atoms.

2. The composition as set forth in claim 1 wherein X and Y both arehydrogen.

3. The composition as set forth in claim 2 wherein R and R are eachhydrogen.

4. The composition as set forth in claim 2 wherein R and R are each acation selected from the group consisting of alkali metals, ammonia,zinc, and mixtures thereof.

5. The composition as set forth in claim 4 wherein the water-solublezinc salt is zinc sulfate and at least one of R and R is sodium.

6. The composition as set forth in claim 1 and additionally containing awater-soluble hexavalent compound of chromium.

7. A composition useful for inhibiting the corrosion of metals in awater system which contains cuprous metals consisting essentially of (1)from about percent to about 90 percent by weight of a substitutedwherein (a) R and R are alike or unlike and are selected from the groupconsisting of hydrogen, metal ions or any cation which will providesufficient solubility in said aqueous system and amine ions (as definedin the specification) and mixtures thereof; (b) R, and R are alike orunlike and are each an alkylene group containing from about two to fivecarbon atoms; (0) X and Y are each alike or unlike and are selected fromthe group consisting of hydrogen aromatic and alkyl; (d) Z is ahydrocarbon group containing from two to 15 carbon atoms, and (e) n hasa value of from 1 through 10; (2) from about 1 percent to about 10percent by weight of a compound selected from the group consisting of1,2,3,-triazoles, thiols of thiazoles, thiols of oxazoles, thiols ofimidazoles, and mixtures thereof, and (3) up to about 79 percent byweight of a water-soluble zinc salt.

8. The composition as set forth in claim 7 and additionally containing awater-soluble hexavalent compound of chromium.

9. A composition useful for inhibiting the corrosion of metals in awater system consisting essentially of from about 2 to about 80 percentby weight ofa silicate and from about 20 percent to about 98 percent byweight of a substituted diamine having the general formula wherein (a) Rand R are alike or unlike and are selected from the group consisting ofhydrogen, metal ions, or any cation which will provide sufficientsolubility in said aqueous system and mixtures thereof; (b) R, and R arealike or unlike and are each independently an alkylene group containingfrom about two to about five carbon atoms; (c) n is an integer having avalue of from about 0 to about 10; (d) X and Y are each alike or unlikeand are selected from the group consisting of hydrogen, aromatic andalkyl; and (e) Z is a hydrocarbon group containing from two to 15 carbonatoms.

10. The composition as set forth in claim 1 wherein the substituteddiamine has the formula CH2CH2OH CHzCHzOH 11. The composition as setforth in claim 1 wherein the substituted diamine has the formula(CIIzCHzO) (CHZCH2() H) (CHzCHzO) (CH2CH2OH) 12. The composition as setforth in claim 1 wherein the substituted diamine has the formula 13. Thecomposition as set forth in claim 1 wherein mmmhu (um-Hm the substituteddiamine has the formula llzOnlllzU llC-Cll omomou H2O3PH2U cmcmou 5 on;em N- CH N orb-om HZOQPHZC CHZCHZOH 20. The composition as set forth inclaim 1 wherein 14. The composition as set forth in claim 1 wherein thesubstituted diamine has the formula the substituted diamine hastheformula lIzOullIzC (Cll'zCHgCHz())(Cll'zClI;Clh()ll) 1:203 P1120 cmcmmomcmon N (CIIZMN momno ]lC-Cl[ ontomemo orncmomon momma cmomo cmomom Q,

(Jug-cu:

15. The composition as set forth in claim 1 wherein the substituteddiamine has the formula 21. The composition as set forth in claim 1wherein the substituted diamine has the formula H;PH2C (CHzCHzCHzO)(CHCHZCHZOH) N(CH2)2N 20 C C HOPHC CHCHO H HOH 111031 1120(CHzCHzCHzO)(CHzCHzCHzOH) a 2 N N HOPHC HC-CH CHCHO CHCHOH 16. Thecomposition as set forth in claim 1 wherein a a 2 2 2 the substituteddiamine has the formula s CHz-CHt HzO PHzO CH CHzOH N (CH2)N 22. Thecomposition as set forth in claim 1 wherein HZOaPHZC CHZCHzOH thesubstituted diamine has the formula IizOaFHflC CHr-GH, CHgCHzOH 17. Thecomposition as set forth '1 claim 1 wherein CH CH CHCH N the substituteddiamine has the formula 1 2- 5 IOaPHzC CH:CH: CHzCHlOH izOgPHzCcmcmoxcmomom N (CH)N K 23. The composition as set forth in claim 1wherein HZOiPHZC (CHZCHEO) (CHQCHZOH) 40 the substituted diamine has theformula HgOaPHgC /CH2CHz (CH2CHz0)(CHzCH-1OH) /N-CHzCH CHCHr-N HzOaPHzCCH2CH2 (cHzcHzoflcHzcHyol-l) 24. The composition as set forth in claim 1wherein 18. The composition as set forth in claim 1 wherein thesubstituted diamine has the formula the substituted diamine has theformula HL-UIhCIIW)(UllzCHzCIlzOII) 25. The method of inhibiting thecorrosion of metals IIZO IHzC N (CH2)BN in a water system comprisingmaintaining in the water HZOKPHZC cmcmcmo clrzomcmou of said system atleast 3 parts per million of a substituted diamine having the generalformula ll lt|()-ll--- (l:\

on Y

N-Z-Nl(lt:i0)n( h ")1! ii i/ 19. The composition as set forth in claim 1wherein 1t|()-l-----(I) 0R2 Y the substituted diamine has the formulawherein (a) R, and R are alike or unlike and are selected from the groupconsisting of hydrogen, metal ions or any cation which will providesufficient solubility in said aqueous system and amine ions (as definedin the specification) and mixtures thereof; (b) R and R are alike orunlike and are each an alkylene group containing from about two to fivecarbon atoms; X and Y are each alike or unlike and are selected from thegroup consisting of hydrogen, aromatic and alkyl; (d) Z is a hydrocarbongroup containing from two to carbon atoms, and (e) n has a value of from1 through 10.

26. The method as set forth in claim 25 wherein X and Y both arehydrogen.

27. The method as set forth in claim 26 wherein R and R are eachhydrogen.

28. The method as set forth in claim 26 wherein R and R are each acation selected from the group consisting of alkali metals, ammonia,zinc, and mixtures thereof.

29. The method as set forth in claim 25 and additionally containing insaid system a water-soluble hexavalent compound of chromium.

30. The method as set forth in claim 25 and additionally containing insaid system a water-soluble zinc salt.

31. The method as set forth in claim 25 and additionally containing insaid system a water-soluble hexavalent compound of chromium and awater-soluble zinc salt.

32. The method as set forth in claim 25 wherein said system containscuprous metals and the water system additionally contains a compoundselected from the group consisting of l,2,3-triazoles, thiols ofthiazoles, thiols of oxazoles, thiols of imidazoles, and mixturesthereof.

33. The method as set forth in claim 32 wherein the water systemadditionally contains a water-soluble zinc salt.

34. A method of inhibiting metal corrosion in a water system containingmetals comprising maintaining in the water of said system (a) from about3 to about ppm of a substituted diaminehaving the formula HzOaPHzCCH2CH2OH or its water-soluble salts and (b) up to about 100 ppm zinc ionderived from water-soluble zinc salts.

2. The composition as set forth in claim 1 wherein X and Y both arehydrogen.
 3. The composition as set forth in claim 2 wherein R1 and R2are each hydrogen.
 4. ThE composition as set forth in claim 2 wherein R1and R2 are each a cation selected from the group consisting of alkalimetals, ammonia, zinc, and mixtures thereof.
 5. The composition as setforth in claim 4 wherein the water-soluble zinc salt is zinc sulfate andat least one of R1 and R2 is sodium.
 6. The composition as set forth inclaim 1 and additionally containing a water-soluble hexavalent compoundof chromium.
 7. A composition useful for inhibiting the corrosion ofmetals in a water system which contains cuprous metals consistingessentially of (1) from about 20 percent to about 90 percent by weightof a substituted diamine having the general formula
 8. The compositionas set forth in claim 7 and additionally containing a water-solublehexavalent compound of chromium.
 9. A composition useful for inhibitingthe corrosion of metals in a water system consisting essentially of fromabout 2 to about 80 percent by weight of a silicate and from about 20percent to about 98 percent by weight of a substituted diamine havingthe general formula
 10. The composition as set forth in claim 1 whereinthe substituted diamine has the formula
 11. The composition as set forthin claim 1 wherein the substituted diamine has the formula
 12. Thecomposition as set forth in claim 1 wherein the substituted diamine hasthe formula
 13. The composition as set forth in claim 1 wherein thesubstituted diamine has the formula
 14. The composition as set forth inclaim 1 wherein the substituted diamine has the formula
 15. Thecomposition as set forth in claim 1 wherein the substituted diamine hasthe formula
 16. The composition as set forth in claim 1 wherein thesubstituted diamine has the formula
 17. The composition as set forth inclaim 1 wherein the substituted diamine has the formula
 18. Thecomposition as set forth in claim 1 wherein the substituted diamine hasthe formula
 19. The composition as set forth in claim 1 wherein thesubstituted diamine has the formula
 20. The composition as set forth inclaim 1 wherein the substituted diamine has the formula
 21. Thecomposition as set forth in claim 1 wherein the substituted diamine hasthe formula
 22. The composition as set forth in claim 1 wherein thesubstituted diamine has the formula
 23. The composition as set forth inclaim 1 wherein the substituted diamine has the formula
 24. Thecomposition as set forth in claim 1 wherein the substituted diamine hasthe formula
 25. The method of inhibiting the corrosion of metals in awater system comprising maintaining in the water of said system at least3 parts per million of a substituted diamine having the general formula26. The method as set forth in claim 25 wherein X and Y both arehydrogen.
 27. The method as set forth in claim 26 wherein R1 and R2 areeach hydrogen.
 28. The method as set forth in claim 26 wherein R1 and R2are each a cation selected from the group consisting of alkali metals,ammonia, zinc, and mixtures thereof.
 29. The method as set forth inclaim 25 and additionally containing in said system a water-solublehexavalent compound of chromium.
 30. The method as set forth in claim 25and additionally containing in said system a water-soluble zinc salt.31. The method as set forth in claim 25 and additionally containing insaid system a water-soluble hexavalent compound of chromium and awater-soluble zinc salt.
 32. The method as set forth in claim 25 whereinsaid system contains cuprous metals and the water system additionallycontains a compound selected from the group consisting of1,2,3-triazoles, thiols of thiazoles, thiols of oxazoles, thiols ofimidazoles, and mixtures thereof.
 33. The method as set forth in claim32 wherein the water system additionally contains a water-soluble zincsalt.
 34. A method of inhibiting metal corrosion in a water systemcontaining metals comprising maintaining in the water of said system (a)from about 3 to about 100 ppm of a substituted diamine having theformula or its water-soluble salts and (b) up to about 100 ppm zinc ionderived from water-soluble zinc salts.